JCLOUDS-774 inconsistent region and zone mappings.

This starts work towards https://issues.apache.org/jira/browse/JCLOUDS-774
yeah I don't like saying the same thing twice. iotw `regionIdToZoneIds.containsKey(regionToURI.getKey())` is a mouthful, as is `regionIdToZoneIds.get(regionToURI.getKey())`